Fixed-mobile communications with mid-session mode switching

ABSTRACT

A method for performing mode-agile communications during a communications session is disclosed. A communications terminal device supporting multiple modes of access is configured to determine when, during a session involving a first mode of access communications, a second mode of access is available and is to be used for subsequent communications for the session. The communications terminal device initiates or controls switchover from one mode of access to another.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 based on U.S.Provisional Application Ser. No. 60/601,256, filed Aug. 13, 2004, thedisclosure of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

Implementations consistent with the invention relate generally toproviding multimode communication and more particularly to providingsession initiation protocol (SIP)-based fixed-mobile convergedcommunication services.

BACKGROUND OF THE INVENTION

Contemporary communication systems may employ wireless and/or wirelinetransmission technologies for conveying data from a source to adestination. Users typically employ different specialized devices foraccessing particular types of communication services, such as voice,data, and/or messaging services. For example, a cellular telephone maybe used to make a wireless voice call, a wireless personal digitalassistant (PDA) may be used to send and receive e-mail messages, afacsimile machine may be used for facsimile transmissions using a plainold telephone system (POTS) landline, and/or a desktop computer mayaccess multimedia applications using digital subscriber line (DSL) overshielded twisted pair. As a result, these transmission-specific ornetwork-specific devices may dictate that users be required to havenumerous devices to perform a range of desired communication functions.The need for multiple devices may add complexity to the provisioning ofrobust communication solutions.

Further complicating communication solutions is the fact that eachdevice may require a unique service agreement, or subscription, with aservice provider. For example, a user may have a service contract with awireless carrier for cellular phone service, a service agreement with aseparate provider for DSL service and still another service agreementfor conventional landline telephone service. The need to have a uniqueidentifier for each device used by a user may add further complexity tocontemporary communication solutions. Each service provider may requirethat a user have a unique identifier associated with its network. Forexample, a user may have one number assigned to them for a cellularphone account, a separate number assigned for a landline account, and ane-mail address, or Ethernet address, assigned for a DSL account. As aresult, the user needs to keep track of these identifiers and may haveto ensure that other parties have these identifiers in order tocommunicate with the user.

It is generally desirable to enable communications among parties viawhatever means or modes of communication are available to them. Forexample, a cellular or wireless user can readily exchange phone callswith PSTN users. However, technologies have yet to be ubiquitouslydeployed wherein a telephone caller may readily communicate with aninstant messaging client on a personal computer for example. Aside froma desire to support cross-communications of this type, it is desirablefor a user to freely employ any mode of communication available, evenusing diverse modes of communication from the same device. Accordingly,some devices recently developed may support multiple modes ofcommunication. For example, an otherwise conventional mobile telephonedevice communicating via 2G or 3G may also be equipped to recognize anearby WiFi ‘hot spot’ and establish communications through the later.

In the context of multimodal communications devices, such as wirelesscommunication devices that can support more than one wireless protocolor carrier frequency band, several modes of communication may sometimesbe available. At any given time and place one type of communication maybe preferred over others due to proximity, low cost, better quality orhigher reliability. However, the choice of a mode of communication iscontrolled by a network, and may occur at any time either uponinitiation of a session or during a session. A so-called ‘mid-callhand-off’, wherein the mode of access changes while a session ismaintained, may take place without warning and may cause a briefinterruption in the communications between parties.

Furthermore, the change from one mode to another, initiated by anetwork-resident entity, may result in a suddenly changing theconnection to one that is less desirable to the user. For example, aconnection with a superior signal strength may exhibit lower bandwidth,lesser security or greater cost. The mid-session switching of accessmodes may occur without regard to the user's desires or preferences,resulting in undesirable operation.

SUMMARY OF THE INVENTION

Various implementations in accordance with the present teachings providefor mid-session changes in access modes to be initiated or moderated bya mobile communications device, in contrast to network-controlledapproaches. Furthermore, various implementations provide for the deviceto carry out such mode switching with due regard for the selection orpreferences of the user of the device.

In accordance with one implementation, a method for conducting acommunications session involving a communication terminal deviceaccessing a network is provided. An exemplary method involves, at thecommunication terminal device, conducting communications correspondingto the session via a first mode of access; determining, at thecommunication terminal device, that a second mode of access is availableto be used for the communications corresponding to the session; from thecommunication terminal device, sending indication to the network thatthe second mode of access is to be used, and, at the communicationterminal device, conducting subsequent communications corresponding tothe session using the second mode of access.

According to another aspect of the present teachings, a communicationdevice is provided which engages in a communications session andconducts communications corresponding to the session via a first mode ofaccess, determines that a second mode of access is available, sendsindication to a network that the second mode of access is to be used forcommunications of the session and conducts subsequent communicationscorresponding to the session using the second mode of access. In someimplementations, the device may send a SIP INVITE message to the networkduring the session to indicate that access mode switchover is to occur.

In accordance with another aspect of the present teachings, a method iscarried out in a communication network for conducting a communicationssession involving a communications terminal device. The method comprisesconducting communications corresponding to the session via a first modeof access between the network and the device; receiving indication fromthe device that a second mode of access between the network and thedevice is to be used for subsequent communications corresponding to thesession; and conducting subsequent communications corresponding to thesession using the second mode of access between the network and thedevice. The degree of mobility of the device enabled by the first modeof access may be substantially different than the mobility enabled bythe second mode of access.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate an embodiment of the inventionand, together with the description, explain the invention. In thedrawings,

FIG. 1 is a block diagram of an exemplary network in which systems andmethods for providing mode-agile communication sessions may beimplemented consistent with the principles of the invention;

FIG. 2 illustrates an exemplary configuration of a general-purposecommunication device that may be used for implementing embodiments ofmultimode communication devices consistent with the principles of theinvention;

FIG. 3 illustrates an exemplary software configuration that may beimplemented in multimode communication devices consistent with theprinciples of the invention;

FIG. 4 illustrates an exemplary implementation of a socket foraccommodating a multimodal communication device consistent with theprinciples of the invention;

FIG. 5 illustrates an exemplary system to facilitate communication witha mobile station traversing across multiple networks while participatingin a SIP based communication session consistent with the principles ofthe invention;

FIG. 6 illustrates an exemplary method for facilitating full featured IPcommunications using SIP based services consistent with the principlesof the invention;

FIG. 7 illustrates an exemplary call flow that may be used to performauthentication and registration in an IP network to provide fixed-mobileconverged communication services consistent with the principles of theinvention;

FIG. 8 illustrates an exemplary call flow that may be used forcompleting a call from a mobile station to a PSTN device consistent withthe principles of the invention;

FIG. 9 illustrates an exemplary call flow originating with a PSTN deviceand terminating at a mobile station consistent with the principles ofthe invention;

FIG. 10 illustrates an exemplary call flow originating at a 2G mobilestation and terminating at a PSTN device after transmission in an IPmode consistent with the principles of the invention;

FIG. 11 illustrates an exemplary call flow that may be used to convey acall from a mobile station to a PSTN device using IP to 2G switchingduring a PSTN call consistent with the principles of the invention;

FIG. 12 illustrates an exemplary call flow that may be used to place auser-to-user call in a 2G mode consistent with the principles of theinvention; and

FIG. 13 illustrates an exemplary call flow that may be used to perform2G to IP mode switching during a calling session consistent with theprinciples of the invention.

DETAILED DESCRIPTION

The following detailed description of implementations consistent withthe principles of the invention refers to the accompanying drawings. Thesame reference numbers in different drawings may identify the same orsimilar elements. Also, the following detailed description does notlimit the invention. Instead, the scope of the invention is defined bythe appended claims and their equivalents.

As used herein, the term ‘access’ generally refers to how a subscriberor user of the communication network is communicably coupled to thenetwork through some form of transmission link. Examples of differentmodes of access are CDPD, 3G, WiMax, WiFi, Ethernet-based LAN/WAN and aconventional telephone subscriber loop. Modes of access may differ interms of, for example, radio frequency band occupied, transmissioncoding and multiplexing schemes, transmission protocols, or propagationmedium used (wireless, wireline, optical, etc.).

The notion of “fixed-mobile convergence” arises in considering how amode-agile device and communication system can carry on a sessions thatuse both high-mobility 2G communications, for example, and low-mobilityWiFi links. Using 2G wireless enables free mobility over a broad areawhereas a given WiFi link is highly localized by comparison and istherefore relatively fixed. Electrical couplings are usually even morelocalized.

The systems and methods may further permit substantially any type offixed and/or mobile communication, such as multimedia, voice, data,messaging, and/or video, to be seamlessly performed, even simultaneouslyin some cases, using a single multimode communication device. Forexample, a single wireless device may be used to place a call viasubstantially any type of network including, but not limited to, aninternet network, 2G/3G mobile networks, time division multiplexed (TDM)networks, wireless networks, such as wireless fidelity (Wi-Fi), andInternet protocol (IP)-based private branch exchange (PBX) systemnetworks. Furthermore, implementations may facilitate switching from onemode of communication to another mode of communication via a requestfrom a subscriber device. The subscriber device may be configured toinitiate mode switching automatically, semi-automatically or manuallyvia user inputs. In some implementations, the user may specify, beforeand outside the context of any particular sessions, when or under whatcircumstances mode switchover is permissible. Various techniques bywhich user preferences may be expressed to, and acted upon by, acommunication device are further described below.

Exemplary Network

FIG. 1 is a block diagram of an exemplary network in which systems andmethods for providing multi-agile communication sessions may beimplemented consistent with the principles of the invention. Network 100may be employed to facilitate communication between wireless and/orwireline devices and may include a wireless local area network (LAN)102, a personal digital assistant (PDA) 104, a network 106, a SIPmobility server 108, a customer premise equipment (CPE) interface 110, adesktop computer 112, a IP telephone 114, a multimode socket 116, ahandheld computer 118, a 2G/3G wireless network 120, a wireless gateway122, a 2G wireless device 124A, a 3G wireless device 124B, a publicswitched telephone network (PSTN) 126, a PSTN telephone 128, and anetwork gateway 130.

Wireless LAN 102 may include any device and/or network capable ofproviding local area connectivity to wireless communication devices,such as PDA 104. Wireless LAN 102 may include network hardware such aswireless routers or access points, switches, network address translators(NATs), etc. Wireless LAN 102 may interface with network 106 via a wiredand/or wireless link. For example, wireless LAN 102 may run a wirelessfidelity (Wi-Fi) protocol such as an IEEE 802.11b protocol. Wireless LAN102 may connect user devices, such as PDA 104, with user devicesoperating on other networks, such as handheld computer 118, 2G wirelessdevice 124A and/or PSTN phone 128.

PDA 104 may include any wireless device capable of processingmachine-readable instructions to perform an operation. For example, PDA104 may include a handheld device having a wireless transceiver forsending and receiving data over a wireless link. PDA 104 may alsoinclude a microprocessor for executing software applications, memory, auser display device, and/or a user input device, such as a touchsensitive display, a keypad, and/or a microphone. PDA 104 may beimplemented as a standalone device or may incorporate functionalityassociated with other devices, such as a wireless phone. PDA 104 may beused to send and receive data to/from one or more wireless networks,such as wireless LAN 102.

Network 106 may include any type of network or even a combination ofnetworks, such as a Wide Area Network (WAN) like the World Wide Web.Network 106 may further include transport and/or network devices such asrouters, switches, and/or firewalls. Network 106 may operate as theprimary transport infrastructure for data sent to, and/or received from,wireless LAN 102, CPE interface 110, wireless gateway 122, and/ornetwork gateway 130. An implementation of network 106 may operate as anInternet protocol (IP) network. Network 106 may cooperatively operatewith other networks running substantially any data networking orcommunications protocols, such as asynchronous transfer mode (ATM),frame relay, synchronous optical network (SONET) or integrated servicesdigital network (ISDN).

Network 106 may support one or more network protocols that can be usedto enhance seamless communication using wireless devices. For example,for session initiation or call set-up, network 106 may support SIP, SIPfor instant messaging and presence leveraging extensions (SIMPLE),single number IP communication protocols such as ENUM, as well as otherprotocols suitable for facilitating multimedia converged services.Network 106 may include a SIP home registrar operating alone, or inconjunction with SIP mobility server 108, for maintaining a database ofnetwork identities associated with fixed and/or mobile devices operatingin network 106.

Network 106 may operate in conjunction with one or more gateways, suchas wireless gateway 122, to determine and/or detect the availability ofwireless devices that are within a signaling range of one or morenetworks associated with network 106. A wireless device that has beendetected by a network and/or gateway may correspond to presenceinformation, implying or indicating availability of an associated enduser to receive communications. Determining presence may includedetecting a wireless device, identifying a wireless device and/ordetermining one or more network protocols that the wireless device iscapable of receiving and/or transmitting. In a similar way, capabilitiesof the device, such as display size, codec schemes or media typessupported, may also be sensed. Network 106 may be configured toautomatically detect and/or communicate with wireless devices based ondynamic registration of the wireless device. This eliminates the needfor manual, explicit registration actions by the user.

SIP mobility server 108 (hereinafter SIP server 108) may include anydevice capable of employing a SIP signaling protocol for creating,modifying and/or terminating sessions, such as IP voice calls and/ormultimedia conference calls. SIP server 108 may be augmented withprivate extensions for allowing other SIP servers to assert theidentities of end users and/or end systems when operating in a trusteddomain. For example, SIP server 108 may operate as a SIP registrar formaintaining a database of user and/or network identifiers, such asURI's. Network identifiers may be used to locate a called party'sdevice. For example, assume that a user may have a unique networkidentifier associated with a wireless SIP phone. Since a mobile devicemay move throughout a network and/or across networks, a SIP registrarmay maintain information associating the network identifier withparticular portions of the network where the wireless SIP phone can bereached at a particular point in time. As the wireless SIP phone movesfrom one location to another, the SIP registrar database may be updatedto reflect a current location of the device. The SIP registrar maymaintain network identifiers for both source devices and destinationdevices to facilitate SIP-based multimode communication sessions.

The use of one or more SIP servers within network 100 may facilitateseamless mode-agile communications. When more than one SIP server isoperating in network 100, one SIP server may operate as a home registrarand other SIP servers may operate as visiting SIP servers.Implementations of the invention may use a single home SIP serveroperating as a home registrar for facilitating mode-agile communicationswithout the need for visiting SIP registrars and/or SIP servers. SIPserver 108 may include additional functionality when acting as the homeregistrar, such as SIP proxy server functionality to facilitate theforwarding of SIP messages across network 100 on behalf of SIP devicesoperating in conjunction with network 100.

CPE interface 110 may include any device capable of communicativelycoupling one or more pieces of customer premise equipment to network106. CPE interface 110 may be associated with one or more customerlocations, such as an office building, university campus, governmentfacility, and/or hospital. CPE interface 110 may include hardware and/orsoftware for coupling customer-owned communication devices to network106. In addition, CPE interface 110 may include security devices such asfirewalls and/or network address translators (NATs). In oneimplementation, CPE interface 110 may further include a customer LANconnecting desktop computer 112 and IP telephone 114 operating inconjunction with multimode socket 116 (hereinafter socket 116), tonetwork 106. CPE interface 110 may aggregate communication data fromdesktop computer 112, IP telephone 114, and/or socket 116 before makingthe data available to network 106.

Desktop computer 112 may include any device capable of processingmachine-readable instructions for performing an operation. Desktopcomputer 112 may include conventional computers, such as personalcomputers, laptops, servers, and/or workstations.

IP telephone 114 may include any telephony device capable of sending andreceiving a telephony voice data stream over a packet network. Examplesare SIP-based IP phones which may be directly coupled to an EthernetLAN. As shown by multimode socket 116, an IP phone appliance may alsoserve as an access point for a multimode communication device. Multimodesocket 116 provides a convenient access point for multimodal devices,with the IP phone acting as a passthrough of sorts. For example, themultimode device may ‘dock’ into the socket to receive networkconnectivity as well as battery recharging, speakerphone or enhanceddisplay capabilities. The multimode device achieves connection throughthe LAN connection of IP phone 114. This arrangement conserves LAN jacksand provides user convenience. If properly equipped, a multimodecommunication device may also establish a Bluetooth wireless connectionwith the IP phone so that no physical or electrical contact needs to beestablished between the devices. The multimode communication device maysense the availability of the Bluetooth link and perform access modeswitching if the user desires. It is contemplated that the multimodedevice may sense the identity of the IP phone and selectively enable theBluetooth access link according to the identity of the IP phone.

IP phone may be part of an ‘IP PBX’ system causing a group of suchphones, such as in a business enterprise, to function as a privatebranch exchange (PBX). A PBX phone may implement a company-internal dialplan and provide for enhanced calling features such as call transfers,call forwarding, conferencing, call pickup and/or support of huntgroups.

Handheld computer 118 may include any device capable of processingmachine-readable instructions to perform an operation. For example,handheld computer 118 may include a palmtop computer having a wirelesscommunication interface for sending and receiving data. Implementationsof handheld computer 118 may operate with wireless LAN 102, 2G/3Gwireless network 120 and/or network 106.

2G/3G wireless network 120 may include any network capable oftransmitting and/or receiving 2G and/or 3G compatible wireless signals.For example, 2G/3G wireless network 120 may be implemented as a cellularnetwork having one or more base stations for transmitting and receivingwireless signals. The base stations may send data to 2G wireless device124A and/or 3G wireless device 124B when a calling party is attemptingto reach a called party associated with one, and/or both, wirelessdevices 124A and 124B.

2G/3G wireless network 120 may include a home location register (HLR)for implementing a database containing subscriber information associatedwith the mobile network. Information contained in an HLR may includesubscriber names, billing information, account status, and/or subscriberdevice information. An HLR may interact with other devices, such as apayment server for performing operational functions, such as billingsubscribers for usage of the wireless network. 2G/3G wireless network120 may include a mobile application part (MAP) proxy to providemobility procedures to SS7 applications. The MAP layer of SS7 mayinclude protocol details that support mobility functions such asregistration, authentication, and/or call completion while providingservice transparency to roaming subscribers. An HLR and/or MAP proxy mayoperate with 2G/3G wireless network 120 to provide 2G services to 2Gwireless device 124A and/or to provide 3G services to 3G wireless device124B.

Wireless gateway 122 may include any device capable of interfacing 2G/3Gwireless network 120 with another network such as wireless LAN 102,network 106, and/or PSTN 126. Wireless gateway 122 may convert 2G/3Gcompatible protocols into IP compatible protocols. Wireless gateway 122may further implement protocols such as SIP when making data availableto network 106. Wireless gateway 122 may receive communication data,process communication data, handoff communication data, and/or performother functions such as error reporting and/or correction.

2G wireless device 124A may include any device capable of sending and/orreceiving 2G compatible data. For example, 2G wireless device 124A mayinclude a 2G compatible cellular telephone, a 2G compatible PDA, and/ora 2G compatible handheld computer. 3G wireless device 124B may includeany device capable of sending and/or receiving 3G compatible data. Forexample, 3G wireless device 124B may include a 3G compatible cellulartelephone, a 3G compatible laptop computer, and/or a 3G compatibleapplication specific device, such as a remote monitoring device.

PSTN 126 may include any network capable of carrying plain old telephonesystem (POTS) compatible data. PSTN 126 may include central officesand/or switches for carrying data over “twisted pair” copper conductorsand/or optical fibers. PSTN 126 may, at various points, accept and carryeither analog signals or digital signals.

PSTN phone 128 may include any device capable of sending and receivingPSTN and/or POTS-compatible data. PSTN phone 128 may be implemented as astandalone device or may be incorporated with other devices, such as adesktop computer having a modem.

Network gateway 130 may include any device capable of converting PSTNand/or POTS compatible data to a format compatible with network 106,wireless LAN 102 and or 2G/3G wireless network 120. Network gateway 130may include hardware and/or software for converting data from a PSTNformat to a format compatible with network 106. Network gateway 130 mayalso include security devices and/or measures, such as firewalls.

SIP-enabled wireless and wireline devices, such as PDA 104, IP telephone114 and/or socket 116, 2G phone 124A, and/or 3G phone 124B, may beconfigured to access all available networks using pertinentcommunication stacks and/or physical network ports associated withavailable networks. For example, communication stacks and/or physicalnetwork ports may be adapted to operate on data received from wirelessLAN 102, network 106, 2G/3G wireless network 120, and/or PSTN network128. Communication stacks may be implemented as software stacks usingexecutable code including callable functions or invoked methods forparsing incoming and/or outgoing messages associated with a particularnetwork protocol. For example, PDA 104 may include a communication stackfor parsing a SIP datagram. Communication stacks may permitcommunication between a client device and one or more networks operatingwith one or more network protocols. SIP-enabled wireless and/or wirelinedevices consistent with implementations of the invention may initiate ahandoff from one communication media, or mode, to another. The handoffmay be initiated based on a location of a device, a user's preference,and/or the types of data exchanged during a communication session. Adevice may initiate change in communication modes upon detecting itsproximity to a point of alternative communication modes or links orotherwise detecting availability of alternative communication modes orlinks.

Exemplary Device Architecture

FIG. 2 illustrates an exemplary configuration of a general-purposecommunication device that may be used for implementing embodiments ofmultimode communication terminal or endpoint devices consistent with theprinciples of the invention. Architecture 200 may be implemented incomputers, network devices and/or non-multimode communication deviceswithout departing from the spirit of the invention. The implementationillustrated in conjunction with FIG. 2 is exemplary and otherconfigurations may alternatively be used.

Architecture 200 may include a processor 220, a bus 222, a memory 230, aread only memory (ROM) 240, a storage device 250, an input device 260,an output device 270, and a communication interface 280. Bus 222 permitscommunication among the components of architecture 200 and may includeoptical or electrical conductors capable of conveying data andinstructions.

Processor 220 may include any type of conventional processor,microprocessor, or processing logic that may interpret and executeinstructions, and may be implemented in a standalone or distributedconfiguration such as in a parallel processor configuration. Memory 230may include a random access memory (RAM) or another type of dynamicstorage device that stores information and instructions for execution byprocessor 220. Memory 230 may also be used to store temporary variablesor other intermediate information during execution of instructions byprocessor 220.

ROM 240 may include a conventional ROM device and/or another staticstorage device that stores static information and instructions forprocessor 220. Storage device 250 may include a magnetic disk or opticaldisk and its corresponding drive and/or some other type of magnetic oroptical recording medium and its corresponding drive for storinginformation and instructions.

Input device 260 may include one or more conventional interfaces,components, and/or mechanisms that permit an operator to inputinformation to architecture 200, such as a keyboard, a mouse, a pen,voice recognition and/or biometric mechanisms, etc. Output device 270may include one or more conventional mechanisms that output informationto an operator and may include a display, a printer, one or morespeakers, etc. Communication interface 280 may include anytransceiver-like mechanism that enables architecture 200 to communicatewith other devices and/or systems. For example, communication interface280 may include a modem or an Ethernet interface to a LAN, a wirelesstransceiver for coupling 3G device 124B to 2G/3G wireless network 120,etc.

Architecture 200 may perform processing in response to processor 220executing sequences of instructions contained in memory 230. Suchinstructions may be read into memory 230 from another computer-readablemedium, such as storage device 250, or from a separate device viacommunication interface 280. It should be understood that acomputer-readable medium may include one or more memory devices, carrierwaves, or data structures, as instructions may be borne on any of thesemedia. Execution of the sequences of instructions contained in memory230 may cause processor 220 to perform certain acts that will bedescribed hereafter in conjunction with method diagrams and signal flowdiagrams. In alternative embodiments, hardwired circuitry may be used inplace of or in combination with software instructions to implementfunctions performed by architecture 200. Yet other embodiments mayinvolve such technologies as Field Programmable Gate Arrays (FPGAs),Application Specific Integrated Circuits (ASICs), dedicated chipsets, orfirmware stored in non-volatile read-only memory. Thus, implementationsconsistent with the invention are not limited to any specificcombination of hardware circuitry and software.

Those of ordinary skill in the art will recognize how various functionsor operations described herein may be implemented in the context of FIG.2. For example, communication interface 280 may monitor the availabilityor relative quality attributes of several potential access links oraccess modes. This information may be provided via bus 222 to processor220, where a running process may decide whether switchover is to takeplace and may initiate switchover by sending signaling to the network asdescribed in later figures. Processor 220 may also execute userinterface applications or processes which use input device(s) 260 andoutput device(s) 270 to interact with the user and receive userpreferences regarding switchover and to inform the user of proposed oractual switchover events. User preferences as to mode switchover may bepersistently stored in storage device 250 or temporarily stored inmemory 230. These preferences may be accessed by processor 220 asdecisions are made affecting switchover.

Exemplary Software Configuration

FIG. 3 illustrates an exemplary software configuration that may beimplemented in multimode communication devices consistent with theprinciples of the invention. Software configuration 300 may include,among other things, operating system 302, applications 304, services306, payments 308, entertainment 310, data 312, interface 314, andnetworking 316. The exemplary software configuration of FIG. 3 may beconfigured to cause a multimode device to initiate a change from onecommunication mode to another during a communication session, especiallywhile maintaining the session in a substantially active state. Thisavoids having to reestablish communications among the communicatingparties whenever a change in access mode is to take place. Ideally, thismode change occurs with little disruption of user communications.

Operating system 302 may include software for controlling the overalloperation and functioning of a wireless and/or wireline multimodecommunication device. For example, operating system 302 may controlscheduling and interactions among applications operating on a wirelessdevice. Operating system 302 may include functionality necessary foraccepting user inputs, such as phone numbers, calendar entries, and/orvoice messages. Operating system 302 may control and/or manage memoryusage, interface usage, and/or diagnostic routines. Implementations ofoperating system 302 may be device specific and may vary depending onthe manufacturer of a particular multimode communication device.

Applications 304 may include one or more software applications includingmachine-executable instructions for performing a function and/or seriesof functions, and/or operations. For example, an application may bedirected to maintaining a calendar on a multimode communication device.Applications 304 may accept user input data and may further synchronizedata with one or more remote applications resident on a server coupledto a network. In particular, some software-encoded applications orprocesses may act to solicit information from the user relative toaccess mode switching, inform the user when access mode switching willoccur or has occurred, and make decisions or comparisons related tochoosing whether to perform access mode switching.

Services 306 may include software having machine-executable instructionsfor facilitating communication between a multimode communication deviceand a destination device providing a service. For example, a service maybe an e-mail service operated by a service provider. The e-mail servicemay operate to deliver messages to and/or receive messages from awireless multimode communication device. Implementations of services 306may include any type of service, such as a real-time traffic reportingcapability for delivering traffic updates to a wireless device based onits location within a service network, real-time stock tradinginformation, real-time weather forecast information based on a locationof the multimode communication device, etc.

Payments 308 may include one or more software applications operating inconjunction with a multimode communication device for making and/orreceiving a monetary transaction. For example, a wireless multimodedevice may run a payment application to make online bill payments via aninteraction with a financial institution.

Entertainment 310 may include a software application for facilitatingthe transmission, receipt and/or display of entertainment related data.For example, an entertainment module may operate on an IP telephone 114having an LCD display associated therewith for displaying movies orderedover a data communication network.

Data 312 may include one or more computer-readable data structurescontaining stored data. Data 312 may include computer-readableinformation associated with substantially any type of application and/orsubject. For example, data 312 may include computer-readable informationdealing with signal strength measurement data received at a wirelessmultimode communication device. For example, a wireless multimode devicemay record received signal strengths from one or more wireless networks.The wireless multimode device may determine which of the wirelessnetworks should be used for a communication session based on the signalstrength data.

Interface 314 may include software to facilitate communication with anetwork using one or more communication protocols. Interface 314 mayinclude machine-readable instructions for converting outgoing data on awireless device into a format compatible with a given network. Forexample, interface 314 may include software that converts outgoing dataon 2G wireless device 124A into a format compatible with 2G/3G wirelessnetwork 120. Interface 314 may convert incoming data into a formatcompatible with 2G wireless device 124A. Interface 314 may includeinstructions for facilitating communication using user datagram protocol(UDP), transmission control protocol (TCP), IP, as well as otherprotocols. Interface 314 may include one more communication stacks forparsing received datagrams. A communication stack may extract data fromincoming datagrams and make the extracted data available to othersoftware routines operating on a multimode communication device.

Networking interface 316 may include machine-readable instructions forimplementing portions of the open system interconnection (OSI) model,namely OSI layers. For example, networking interface 316 may facilitateimplementation of the physical layer (layer 1) and/or data link layer(layer 2) of the OSI model for allowing a multimode communication deviceto communicate with a network running a particular networking protocol.Networking interface 316 may operate in conjunction with hardware suchas a network interface card (NIC). Networking interface 316 may operateto cause a multimode device to change from one communication mode toanother based on an instruction initiated by a multimode device and/or auser thereof.

Multimode communication devices may include other software functionalityas necessary for accommodating the needs of users and/or integrationwith various network types. Furthermore, multimode communication devicesmay employ software in a standalone mode, where an entire softwareapplication is resident on the communication device, and/or in adistributed mode, where a portion of the software is resident on thecommunication device while the remaining software is accessed remotelyusing a network connection.

Exemplary Communications Socket

FIG. 4 illustrates an exemplary implementation of a multimode socket forcoupling with a multimode communications device. In some designsconsistent with the present invention, the communication device mayphysically ‘nest’ into, or mechanically couple to, the socket, althoughit should be understood that this is not a requirement in accordancewith the present invention. The communications device may also achievesome electrical connection with the socket when coupled thereto. Theelectrical connection may provide for analog or digital signals as wellas direct current flow, which may be useful for power in the deviceand/or recharging batteries of the device. The communications device mayalso, or alternatively, employ short-range radio signals or opticalsignals to pass communications via the socket. In figure four, amultimode communications device 200 is shown be coupled to socket 116through interface 414. Interface 414 may comprise any mixture ofmechanical, electrical, electromagnetic or optical couplings as neededfor a given design.

Socket 116 may include, among other things, a battery charger 402, aPC/laptop synchronization module 404, an Ethernet interface 406, adisplay device 408, a speaker 410 and/or a microphone 412.

Battery charger 402 may include any device capable of recharging abattery. Battery charger 402 may be configured and arranged to operateas a cradle for accepting a communication device, such as 2G wirelessdevice 124A. Battery charger 402 may recharge a battery associated with2G wireless device 124A and may include electrical components and/oroptical media for communicating data to and/or receiving data from 2Gwireless device 124A while charging. For example, a high bandwidthoptical fiber in socket 116 may removeably couple to a correspondingoptical fiber connector associated with 2G wireless device 124A whenmounted on battery charger 402. 2G wireless device 124A may be capableof participating in high bandwidth multimode communications with aremote device via CPE interface 110 and socket 116 while engaged withbattery charger 402. Alternatively, 2G wireless device 124A maycommunicate with socket 116 using a free-space wireless protocol such asBluetooth.

PC/laptop synchronization module 404 may communicate with mobile device200 (such as a PDA) to enable synchronization and reconciliation ofe-mail files, calendar data and address book data among the mobiledevice 200 and the relatively fixed PC or laptop computer. A laptop maycommunicate with socket 116 using a hardwired connection or a free spacelink such as an infrared link and/or a short-range wireless link.

Ethernet interface 406 may include a connector and/or logic forcommunicatively coupling socket 116 to IP telephone 114 and/or directlyto CPE interface 110 to provide the mobile device a direct LANconnection as an available mode of access. Ethernet interface 406 mayinclude an industry standard RJ-45 receptacle for removeably couplingsocket 116, to an Ethernet network, for example.

Display device 408 may include any type of display, such as a colorliquid crystal display (LCD), to provide a display capability to adevice, such as 2G wireless device 124A. Display device 408 mayfacilitate display of high resolution video and/or images while 2Gwireless device 124A is operatively coupled to socket 116.

Speaker 410 and/or microphone 412 may provide speakerphone and/orenhanced audio capabilities to a device, such as 2G wireless device124A, while operatively coupled to socket 116. For example, 2G wirelessdevice 124A may provide identification information to SIP mobilityserver 108 using socket 116 so that a user associated therewith canparticipate in a video conference requiring greater bandwidth than thatprovided by a 2G wireless network. Socket 116 may be configured to allowa conventional device and/or a multimode device to initiate a changefrom one type of media session to another during a communicationsession. Socket 116 may perform necessary communications with networkdevices to facilitate the change in media types or media parameters(bandwidth, codec scheme, resolution, etc.).

Exemplary System for Sip-Based Mobile Communication

FIG. 5 illustrates an exemplary system to facilitate communication witha mobile station traversing across multiple networks while participatingin a SIP based communication session consistent with the principles ofthe invention. For example, a mobile station participating in acommunication session may traverse from a first network operating with afirst network protocol to a second network operating with a secondnetwork protocol without interrupting the communication session. Thefirst network and the second network may both be wireless networks withthe first network being a cellular network and the second network beinga wireless-IP network, such as a Wi-Fi network. Implementationsconsistent with the principles of the invention may allow a mobilestation to traverse from the first network to the second network withoutinterrupting an ongoing communication session taking place between themobile station and a destination device. Implementations consistent withthe principles of the invention may let a mobile device initiate achange from one network to another and/or from one communication mode toanother.

System 500 may include network 106, a mobile station 502 having astarting location 504 and an ending location 506, a first foreignnetwork 508, a second foreign network 510, a participating station 512,a home registrar and proxy server 514 (hereinafter home SIP registrar514), and a home network 516.

Network 106 may include a network substantially similar to network 106described in conjunction with FIG. 1. In one implementation, network 106is a public network, such as the Internet.

Mobile station 502 may include any wireless device capable ofparticipating in a multimode communication session. Mobile station 502may commence a SIP based communication session with participatingstation 512 via first foreign network 508 at starting location 504.While engaged in communication via first foreign network 508, mobilestation 502 may move toward a second foreign network 510. Second foreignnetwork 510 may be positioned and may be capable of communicating withmobile station 502 at an ending location 506. First foreign network 508and second foreign network 510 may be operatively coupled to network 106via a gateway.

Mobile station 502 may be configured to initiate a transition from firstforeign network 508 to second foreign network 510. Mobile station 502may request the change based on one or more attributes by which the twonetworks may be compared. These relative attributes may include, forexample, signal strength or signal/noise ratio, bit error rate,bandwidth, physical proximity, quality, reliability, cost, level ofsecurity, capabilities supported.

In some implementations, user preferences may affect how theseattributes are weighed into the decision to switch from one network toanother or one mode of access to another. For example, a user mayexpress a threshold at which the differences between the networks arecompelling enough to justify switchover. Alternatively or additionally,a user preference may be expressed and carried out in terms of a givenmode of access or identity of given network that is preferred overanother. These preferences may be specified well before, and outside thecontext of, any particular communications sessions.

User preferences may be maintained in persistent storage or non-volatilememory in the mobile device. User preferences may be retained at a pointremote from the device and made available to the device as needed orupon power-up or registration of the device with a network.

In a semi-automatic mode, the device may determine that a viable ordesirable alternative network or mode of access is available and thenprompt the user for permission to perform the switching. This approachallows the user to participate in the decision and to even control thetiming of the switchover to coincide with a break in the conversation,for example. Upon receiving the user's decision to proceed, the devicethen performs signaling, as described later herein, to initiate theswitchover.

Whether or not user preferences are considered for switchover decisionsand whether or not the user input is solicited in ‘real time’ during asession, the device may notify the user that such switchover has takenplace or will be taking place. This may enhance the user's awareness ofmid-session switching. It is envisioned that the notification from thedevice may be in the form of visual or audible stimulus or evenmechanical motion, such as a momentary vibration. For example, a personusing a mobile telephone as a handset in the vicinity of their ear andmouth may not be able to see the display, but could receive a slightvibration during a conversation, the vibration having a characteristicpattern and subtly indicating that access mode switching has occurred.The user may want to be aware of shifts in cost or of when momentarysignal interruption may have occurred affecting the reception of spokenwords through the connection.

When executing a mid-session mode switchover, the device may signal tothe user when the new connection has been successfully established.Alone or in conjunction with other interactions described above, thisfeature may be useful in some implementations for clarifying to the userwhen they have achieved a reliable connection after switchover.

It is possible to combine some of the above approaches. The device mayemploy user preferences configured beforehand to affect whether analternative connection is adequate to considering switchover and thenprompt the user for permission to execute the switchover.

User preferences affecting switchover from one access mode to another orone network to another may be entered in a variety of ways. The user mayenter preferences into the device directly, such as by interaction witha user interface application presented by the device (such as anapplication 304). Beforehand user preferences may be entered through,for example, a web site which is able to populate a user profile whichmay then be made available to the device and/or the network for makingswitchover decisions. Real-time conditions, such as detected wirelesssignals, may be evaluated relative to criteria either entirely withinthe device or cooperatively with other elements.

Depending upon implementation, user preferences may be simple ordetailed. One form of user preference may simply express whether themobile device is enabled to perform automatic or semi-automaticswitching of access modes. Alternatively, user preferences may expressdetail as to criteria or threshold conditions under which mode switchingis to take place. The present invention is not limited in scope to aparticular one of these variations and which variations are deployed inpractice adopted may be a matter of design choice.

One aspect of user preferences which may be useful in some situations isa time delay or persistence value. This value relates to the interval oftime that an alternative link, network or mode of access must bepersistently detected as being available before the device will considerit as a candidate for subsequent communications. This avoids undesirabletransient switchovers that might occur when a mobile user momentarilypasses by public WiFi hotspots, for example. The time delay may beprogrammable by the user, even to the extent of having differentiatedthresholds as a function of network type, network identity, etc.

Continuing to refer to FIG. 5, first foreign network 508 and secondforeign network 510 may include any type of wireless network capable ofsending data to a mobile station and/or capable of receiving data from amobile station. First and second foreign networks 508, 510 may operateusing a single wireless networking protocol or may operate usingdifferent wireless networking protocols. First and second foreignnetworks 508, 510 may receive data from network 106 and/or make dataavailable to network 106. For example, first foreign network 508 mayreceive a dialed number associated with a called party from mobilestation 502. First foreign network 508 may make the dialed numberavailable to network 106 so that home SIP registrar 514 can determine alocation associated with the called party in order to complete the callon behalf of mobile station 502.

Participating station 512 may include any device capable of sending datato a network and/or capable of receiving data from a network.Participating station 512 may include communication devices such as PDA104, handheld computer 118, 2G wireless device 124A, and/or PSTN phone128. Participating station 512 may operate as a source device whenmaking a call and/or as a destination device when receiving a call.

Home SIP registrar 514 may include any device capable of beingconfigured and operated as a home location registrar on a network. HomeSIP registrar 514 may be implemented in a standalone configurationand/or may be combined with SIP mobility server 108. Home SIP registrar514 may be coupled to home network 516 and/or to network 106. Home SIPregistrar 514 may operate to affect communications between mobilestation 502 and/or the respective networks over which mobile station 502may communicate. Home SIP registrar 514 may perform functions, such asdetermining optimum paths for conveying data from mobile station 502 toone or more participating stations 512. For example, home SIP registrar514 may facilitate a handoff from first foreign network 508 to secondforeign network 510 using network layer 2, as mobile station 502 reachesthe edge of a coverage area associated with first foreign network 508.Home SIP registrar 514 may further connect mobile station 502 with homenetwork 516.

Home network 516 may include a primary network associated with mobilestation 502. Home network 516 may be configured to receive data from acommunication device when the device is associated with a location thatis within a coverage area of home network 516.

Communication may take place, using system 500, when mobile station 502sends a SIP-compliant INVITE, or re-INVITE, request to first foreignnetwork 508. The INVITE request may operate as a request to have adestination device participate in a communication session with mobilestation 502. The INVITE request may include a ‘Contact’ header field andan updated Session Description Protocol (SDP) that may define atext-based format for describing a streaming media session and/ormulticast transmission. First foreign network 508 may issue a message,such as a 200 OK response, to indicate that an INVITE request has beenreceived and understood.

Mobile station 502 may issue an acknowledgement, such as an ACK responseto confirm that it has received the 200 OK response. Mobile station 502may send data to, and/or receive data from, first foreign network 508after sending the acknowledgement. For example, a SIP-enabledcommunication session may take place using the data exchanged betweenmobile station 502 and first foreign network 508, after the INVITE, 200OK, and ACK message exchange has occurred.

The INVITE, 200 OK, and ACK syntax for establishing a communicationsession may be used by other devices in system 500. For example, firstforeign network 508 may send an INVITE request to network 106, network106 may send a 200 OK response to first foreign network 508, and firstforeign network 508 may send an acknowledgement to network 106. Afterthe above exchange, first foreign network 508 and network 106 mayexchange communication data as part of a communication session. Devicesassociated with implementations of the invention may use SIP fornegotiating parameters associated with fixed and/or mobile communicationsessions.

Exemplary Method for Sip-Based Communication

FIG. 6 illustrates an exemplary method for facilitating full featured IPcommunications using SIP-based services consistent with the principlesof the invention. The method may commence when a mobile device, such asmobile station 502, requests an IP address using dynamic hostconfiguration protocol (DHCP) (act 602). Mobile station 502 may requestan IP address so that it has a network identifier that can be used forestablishing its identity on one or more networks. Mobile station 502may establish a network connection and may commence communication usingthe obtained IP address (act 604). For example, an IP address mayoperate to identify mobile station 502 to other devices on a network.Network devices such as routers, firewalls and/or switches may use theIP address for allowing data sent from mobile station 502 to pass acrossa network. Network devices may also use the IP address to deliver datato mobile station 502. An optimum NAT/firewall traversal route may bedetermined using techniques known in the art (act 606). For example, atraversal route may be determined using ICE, STUN, TURN and/orrealm-specific IP (RSIP).

Mobile station 502 may register with its home SIP registrar (act 608).For example, mobile station 502 may register with home SIP register 514.Registration may operate to provide the home SIP registrar withinformation regarding the identity of the mobile station 502 and/or itscurrent location. Registration may also include an exchange ofinformation about a configuration associated with mobile station 502.For example, registration may provide home SIP registrar 514 withinformation about the types of media sessions that mobile station 502can support.

Mobile station 502 may commence full SIP-based IP communication over anetwork (act 610). Mobile station 502 may commence a communicationsession with participating station 512. For example, home SIP registrar514 may include a network identifier associated with participatingstation 512. Mobile station 502 may issue an INVITE request toparticipating station 512 to request that participating station 512 joina communication session with mobile station 502. Home SIP registrar 514may receive the INVITE request from mobile station 502 and forward therequest to participating station 512. Participating station 512 may senda 200 OK response to mobile station 502 via home registrar 514 toacknowledge that the INVITE request was received. Mobile station maysend an acknowledgement message, such as an ACK message, directly toparticipating station 512 to acknowledge receipt of the 200 OK message.Mobile station 502 may send the ACK message directly to participatingstation, without passing through home SIP registrar 514, because mobilestation 502 may have obtained the network identifier for participatingstation 512 from the 200 OK message received via home registrar 514.

Home SIP registrar 514 and/or one or more traversed networks may operateto determine if mobile station 502 is attempting to switch between twonetworks (act 612). For example, home SIP registrar 514 may operate withfirst foreign network 508, second foreign network 510 and/or network 106to determine if mobile station 502 is making a request and/or attemptingto switch from first foreign network 508 to second foreign network 510.If first foreign network 508 or second foreign network 510 detect thatmobile station 502 is attempting to switch networks, first foreignnetwork 508 and/or second foreign network 510 may contact home SIPregistrar 514. First foreign network 508 and/or second foreign network510 may inform home SIP registrar 514 that mobile station 502 is movingfrom one network to another.

When mobile station 502 is attempting to switch networks, a SIPre-INVITE request may be issued without causing any interruption in theestablished Internet communication session (act 614). For example,mobile station 502 and/or second foreign network 510 may issue are-INVITE request to home SIP registrar 514. Mobile station 502 may sendthe re-INVITE request automatically and/or a user of mobile station 502may manually cause the re-INVITE request to be sent. The re-INVITErequest may be used by home SIP registrar 514 to continue thecommunication session using second foreign network 510 instead of firstforeign network 508. For example, home SIP registrar 514 may operatealone or with other network devices to transition the portion of acommunication session traversing first foreign network 508 onto secondforeign network without interrupting the communication session. Incontrast, if mobile station 502 is not trying to switch networks, methodflow may return to act 610.

Implementations consistent with the principles of the invention make itpossible for mobile station 502 to move from first foreign network 508to second foreign network 510 without suffering any interruption in anongoing communication session. Furthermore, a user of mobile station 502may not have to perform any manual operations with respect tomaintaining connectivity during the session since system 500 may performrouting and switching automatically. In addition, an implementation mayemploy a single home SIP registrar 514 thus alleviating the need foremploying a visiting SIP registrar. Use of a single SIP registrar mayensure that seamless communication sessions are possible.

Exemplary Authentication and Registration Call Flow

FIG. 7 illustrates an exemplary call flow that may be used to performauthentication and registration in an IP network to provide fixed-mobileconverged communication services consistent with the principles of theinvention. Call flow 700 may take place among a multimode mobile station702, a visited access point/Ethernet switch 704, a visited RADIUS/AAAserver 706, an AAA server 708, a STUN/TURN server 710 and a SIP proxyserver 712.

Multimode mobile station 702 (hereinafter mobile station 702) mayinclude any device capable of supporting more than one mode of wirelesscommunication. For example mobile station 702 may include mobile station502. Visited access point/Ethernet switch 704 (hereinafter access point704) may include any device capable of operating as a wireless accesspoint in a network. For example, access point 704 may be included in2G/3G wireless network 120, first foreign network 508 and/or secondforeign network 510. Visited radius AAA server 706 (hereinafter visitedserver 706) may include any device capable of performing authentication,authorization and accounting (AAA) services and/or remote authenticationdial-in user service (radius). Visited server 706 may allow remoteaccess servers to access a central server for authorizing users of anetwork. Visited server 706 may operate with one or more databasescontaining user information when performing authorization operations.Visited server 706 may be implemented as a standalone device and/or maybe incorporated into the functionality of another device, such as SIPmobility server 108 and/or home SIP registrar 514. AAA server 708 mayinclude any device capable of performing AAA services. STUN/TURN server710 may include any device capable of performing simple traversal of UDPthrough NAT's (STUN) and/or traversal using relay NAT (TURN) services.STUN/TURN server 710 may operate to facilitate network traversal ofsignaling and/or messaging data associated with facilitatingcommunication sessions between a source device and a destination. AAAserver 708 and/or STUN/TURN server 710 may be implemented as networkdevices operating in network 106, wireless gateway 122 and/or networkgateway 130. SIP proxy server 712 may include any device capable offacilitating SIP based communication sessions. For example, SIP proxyserver 712 may be implemented as part of SIP mobility server 108 and/orhome SIP registrar 514. SIP proxy server may operate to forward SIPmessages on behalf of a source device and/or a destination deviceassociated with a communication session.

Mobile station 702 may issue an extensible authentication protocol (EAP)message 714 in an IEEE 802.1x format that is compatible with a wirelessnetwork protocol to initiate a communication session. EAP may be used toassist a network device with selecting an appropriate network accessidentifier (NAI). An NAI may be an identifier for use in establishingthe identity of a device on a network. An NAI may identify a roamingdevice that may not be associated with its home network.

A compatible IEEE 802.1x access point 704 may receive an EAP message 714and may forward EAP message 716 via a radius compatible format tovisited server 706. Visited server 706 may send a request 718 to AAAserver 708. Request 718 may indicate that mobile station 702 desires toregister with a network. AAA server 708 may send an answer 720 tovisited server 706 in response to request 718. Visited server 706 maygenerate a response 722 that is sent to access point 704. Response 722may be generated as a result of EAP message 716. Access point 704 maypass an EAP success message 724 to mobile station 702. EAP successmessage 724 may indicate that a request to register was acknowledged.

Mobile station 702 may send a DHCP discovery/offer message 726 to accesspoint 704. A STUN/TURN protocol compliant path 728 may be establishedbetween mobile station 702 and STUN/TURN server 710. Mobile station 702may send a register request 730 to SIP proxy server 712. SIP proxyserver 712 may send a 200 OK response 732 indicating that the registerrequest 730 was received and understood. SIP proxy server 712 mayoperate to register mobile station 702 on a network, such as network106, using signal flow 700. After registering on a network, mobilestation 702 may be able to participate in multimode communicationsessions with a destination device.

Exemplary Mobile Station to PSTN Call Flow

FIG. 8 illustrates an exemplary call flow that may be used forcompleting a call from a mobile station to a PSTN device consistent withthe principles of the invention. Call flow 800 may take place among amultimode mobile station 702, a cellular mobile switch 802, a mobilegateway 804, a SIP proxy server 712, a PSTN gateway 806 and a PSTNdevice 808.

Mobile station 702 and SIP proxy server 712 may be configuredsubstantially as described in conjunction with FIG. 7. Cellular mobileswitch (hereinafter mobile switch 802) may include any device capable offacilitating the setup of a wireless call. For example, mobile switch802 may operate as part of first foreign network 508 and/or secondforeign network 510 to process an outgoing string of digits associatedwith the identity of a called party. Mobile gateway 804 may include anydevice capable of interfacing a wireless network with another network.For example, mobile gateway 804 may be configured to operate in a mannersubstantially similar to wireless gateway 122 discussed in connectionwith FIG. 1. PSTN gateway 806 may include any device capable ofinterfacing a PSTN network with another network. In one implementation,PSTN gateway 806 may be configured to operate in a manner substantiallysimilar to network gateway 130 discussed in connection with FIG. 1. PSTNdevice 808 may include any device capable of making or receiving PSTNcalls. In one implementation, PSTN device 808 may be configured tooperate in a manner substantially similar to PSTN phone 128.

Call flow 800 may commence when mobile station 702 issues a call attemptusing a string of dialed digits 810. Mobile switch 802 may receivedialed digits 810 and construct an initial address message (IAM), orsetup message, 812. IAM 812 may include the dialed digits received frommobile station 702. Mobile switch 802 may send IAM 812 to mobile gateway804. Mobile gateway 804 may send an INVITE request 814 to SIP proxyserver 712. INVITE request 814 may operate as a request to have adestination device, such as PSTN device 808, participate in a callingsession with mobile station 702. SIP proxy server 712 may forward INVITErequest 814 to PSTN gateway 806 as INVITE request 816.

PSTN gateway 806 may issue a 200 OK response 818 indicating that INVITErequest 816 was received and understood. SIP proxy server 712 mayreceive 200 OK response 818 and may generate 200 OK response 820 andsend it to mobile gateway 804 to indicate that INVITE request 814 wasreceived and understood. Mobile gateway 804 may send an ANM or connectmessage 822 to mobile switch 802. Mobile switch 802 may issue a connectmessage 824 to mobile station 702. Mobile station 702 may communicateover the network with media over cellular data 826. Mobile station 702may transmit media over cellular data 826 to mobile switch 802. Mobileswitch 802 may pass media data 828 to mobile gateway in a TDM format.Mobile gateway 804 may convert media data 828 to an IP format 830 andmay convey the data to PSTN gateway 806. PSTN gateway 806 may providemedia data to PSTN device 808 in a PSTN compatible format 832.

Exemplary PSTN to Mobile Station Call Flow

FIG. 9 illustrates an exemplary call flow originating with a PSTN deviceand terminating at a mobile station consistent with the principles ofthe invention. Call flow 900 may use mobile station 702, mobile switch802, mobile gateway 804, SIP proxy server 712, PSTN gateway 806 and PSTNdevice 808. Mobile station 702, mobile switch 802, mobile gateway 804,SIP proxy server 712, PSTN gateway 806 and PSTN device 808 may beconfigured as previously described.

PSTN gateway 806 may send an INVITE request 902 to SIP proxy server 712.SIP proxy server 712 may forward INVITE request 902 to mobile gateway804 as INVITE request 904. Mobile gateway 804 may send an IAM or setupmessage 906 to mobile switch 802. Mobile switch 802 may send an alertingsignal 908 to mobile station 702. An alerting signal may include, forexample, a ring tone.

Mobile station 702 may issue an answer 910 based on alerting signal 908.For example, a user may respond to alerting signal 908 by answering thephone. Alternatively, an alerting signal 908 may be addressed by havingan answering machine and/or voice mail system pick up the incomingsignal. Mobile switch 802 may receive answer 910. Mobile switch 802 mayissue an ANM or connect message 912. Mobile gateway 804 may receive ANMor connect message 912 and may send a 200 OK response 914 to SIP proxyserver 712. 200 OK response 914 may indicate that INVITE request 904 wasreceived and understood. SIP proxy server 712 may send a 200 OK response916 to PSTN gateway 806 indicating that INVITE request 902 was receivedand understood.

PSTN gateway 806 may respond to 200 OK response 916 by sending anacknowledgement response ACK 918 to SIP proxy server 712. SIP proxyserver 712 may send an acknowledgement response as ACK 920 to mobilegateway 804 indicating that 200 OK response 914 was received andunderstood. When mobile gateway 804 receives ACK 920, a media overcellular call 922 may be enabled. Mobile switch 802 may pass cellularmedia data 922 to mobile gateway 804 in a TDM format 924. Mobile gateway804 may pass media over IP 926 to PSTN gateway 806 which in turn mayconvey the data to PSTN device 808 in a PSTN format 928.

Exemplary Mode Switching 2G to IP Mode Call Flow

FIG. 10 illustrates an exemplary call flow originating at a 2G mobilestation and terminating at a PSTN device after transmission in an IPmode consistent with the principles of the invention. Call flow 1000 mayinclude a mobile station 702, an access point 704, a mobile switch 802,a mobile gateway 804, a SIP proxy server 712, a PSTN gateway 806 and aPSTN device 808. Mobile station 702, access point 704, mobile switch802, mobile gateway 804, SIP proxy server 712, PSTN gateway 806 and PSTNdevice 808 may operate as previously described.

An implementation of call flow 1000 may initially include media overcellular 1002, media over TDM 1004, media over IP 1006 and media overPSTN 1008. During a call, call flow 1000 may transition so as to includemedia over IP 1038 and PSTN media 1040. The transition may occur as aresult of a request made by a mobile device, such as mobile station 702.

Call flow 1000 may commence when an 802.1x authorization message 1010 isexchanged between mobile station 702 and access point 704. A SIPregistration STUN/TURN message 1012 may be exchanged between mobilestation 702 and SIP proxy server 712. SIP registration STUN/TURN message1012 may traverse one or more NATs and/or firewalls en route to SIPproxy server 712. Mobile station 702 may issue an INVITE request 1014 toSIP proxy server 712. INVITE request 1014 may operate as a request, orinvitation, to a destination device to join a calling session withmobile station 702, such as media over IP session 1038. SIP proxy server712 may send INVITE request 1016 to PSTN gateway 806. INVITE request1016 may include a ‘Replaces’ header that may include informationassociated with transitioning the ongoing communication session to mediaover IP 1038.

PSTN gateway 806 may respond to INVITE request 1016 with a 200 OKresponse 1018 indicating that the INVITE request was received andunderstood. SIP proxy server 712 may send a 200 OK response 1020 tomobile station 702. Mobile station 702 may send an acknowledgement (ACK)response 1022 to SIP proxy server 712 to acknowledge receipt of 200 OKresponse 1020. SIP proxy server 712 may send an ACK response 1024 toPSTN gateway 806. ACK response 1024 may indicate that 200 OK response1018 was received and understood.

PSTN gateway 806 may send a BYE request 1026 to SIP proxy server 712 toterminate a portion of the communication session. SIP proxy server 712may send a BYE request 1028 to mobile gateway 804. Mobile gateway 804may send a release message 1030 to mobile switch 802. Release message1030 may be associated with releasing, or terminating, a portion of thecurrent communication session. Mobile switch 802 may send a disconnectmessage 1032 to mobile station 702. Disconnect message 1032 may cause aportion of the calling session to terminate. When mobile gateway 804receives BYE request 1028, it may return 200 OK response 1034 to SIPproxy server 712. SIP proxy server 712 may send a 200 OK response 1036to PSTN gateway 806. The communication session may include media over IP1038 between mobile station 702 and PSTN gateway 806 and PSTN databetween PSTN gateway 806 and PSTN device 708.

Exemplary IP to 2G Mode Switching Call Flow

FIG. 11 illustrates an exemplary call flow that may be used to convey acall from a mobile station to a PSTN device using IP to 2G switchingduring a PSTN call consistent with the principles of the invention. Callflow 1100 may use a mobile station 702, an access point 704, a cellularmobile switch 802, a mobile gateway 804, a SIP proxy server 712, a PSTNgateway 806 and a PSTN device 808. Mobile station 702, access point 704,cellular mobile switch 802, mobile gateway 804, SIP proxy server 712,PSTN gateway 806 and PSTN device 808 may be configured and may operateas previously described.

Call flow 1100 may initially include media over IP 1102 between mobilestation 702 and PSTN gateway 806 and a PSTN call 1103 between PSTNgateway 806 and PSTN device 808. During a communication session, callflow 1100 may transition to media over cellular 1130 between mobilestation 702 and mobile switch 802, media over TDM 1132 between mobileswitch 802 and mobile gateway 804, media over IP 1134 between mobilegateway 804 and PSTN gateway 806, and a PSTN call 1136 between PSTNgateway 806 and PSTN device 808. The transition may be initiated as aresult of actions performed by a subscriber device, such as mobilestation 702 and/or PSTN device 708.

Call flow 1100 may include a call attempt having dialed digits 1104between mobile station 702 and mobile switch 802. Mobile switch 802 mayissue an IAM or setup message 1106 to mobile gateway 804. IAM message1106 may include the dialed digits. Mobile gateway 804 may send anINVITE request 1108 to SIP proxy server 712. SIP proxy server 712 maysend an INVITE request including a ‘Replaces’ header 1110 to PSTNgateway 806, where the ‘Replaces’ header may operate to substitute anetwork identifier associated with one device with that of another. Forexample, INVITE request 1108 may include a network identifier associatedwith the sending device, here mobile gateway 804. When SIP proxy server712 sends INVITE request 1110, the ‘Replaces’ header may include anetwork identifier associated with SIP proxy server 712 and/or anotherdevice on the network. INVITE requests using a ‘Replaces’ header mayfacilitate operations, such as call pickup, call forwarding, and callhandoffs. PSTN gateway 806 may respond with a 200 OK response 1112. SIPproxy server 712 may receive 200 OK response 1112 and may issue a 200 OKresponse 1114 to mobile gateway 804.

Mobile gateway 804 may send an ANM or connect message 1116 to mobileswitch 802. Mobile switch 802 may issue a connect message 1118 toestablish a call with mobile station 702. Mobile gateway 804 may issuean ACK reply 1119 to SIP proxy server 712 to acknowledge receipt of 200OK response 1114. SIP proxy server 712 may send an ACK reply 1120 toPSTN gateway 806 to acknowledge receipt of 200 OK response 1112.

PSTN gateway 806 may issue a BYE request 1122 that may be sent to SIPproxy server 712. SIP proxy server 712 may send a BYE request 1124 tomobile station 702 to disconnect a portion of the current communicationsession. SIP proxy server 712 may receive a 200 OK response 1126 frommobile station 702 acknowledging receipt of BYE request 1124. SIP proxyserver 712 may send 200 OK response 1128 to PSTN gateway 806 toacknowledge receipt of BYE request 1122.

Exemplary User to User Call Flow

FIG. 12 illustrates an exemplary call flow that may be used to place auser-to-user call in a 2G mode consistent with the principles of theinvention. Call flow 1200 may include a first dual mode mobile station702A, a second dual mode mobile station 702B, a cellular mobile switch802, a mobile gateway 804 and a SIP proxy server 712. First mobilestation 702A and second mobile station 702B may be configured to operatein a manner substantially similar to mobile station 702. Mobile switch802, mobile gateway 804 and SIP proxy server 712 may be configured tooperate as previously described.

Call flow 1200 may commence when a call attempt including dialed digits1202 is initiated between first mobile station 702A and mobile switch802. Mobile switch 802 may send an IAM or setup message 1204 includingdialed digits to mobile gateway 804. Mobile gateway 804 may send anINVITE request 1206 to SIP proxy server 712. INVITE request 1206 mayoperate to INVITE second mobile station 702B to join a communicationsession. SIP proxy server 712 may send an INVITE request 1208 to mobilegateway 804 in response to INVITE request 1206.

Mobile gateway 804 may send an IAM or setup message 1210 includingdialed digits to mobile switch 802. Mobile switch 802 may issue analerting message 1212 to second mobile station 702B. Second mobilestation 702B may answer the alerting signal by answering the phone.Mobile switch 802 may send an ANM or connect message 1214 to mobilegateway 804 after issuing alerting message 1212 and/or detecting thatsecond mobile station 702B has picked up the call. Mobile gateway 804may send a 200 OK response 1216 to SIP proxy server 712 in response toreceiving INVITE request 1208. SIP proxy server 712 may return a 200 OKresponse 1218 to acknowledge the receipt of INVITE request 1206.

Mobile gateway 804 may send an ANM or connect message 1220 to mobileswitch 802. Mobile switch 802 may commence a calling session usingconnect message 1222. Mobile switch 802 may send connect message 1222 tofirst mobile station 702A. The calling session may take place betweenfirst mobile station 702A and second mobile station 702B. Mobile gateway804 may send ACK response 1228 to SIP proxy server 712 to acknowledgereceipt of 200 OK response 1218. SIP proxy server 712 may send an ACKresponse 1230 to mobile gateway 804 to acknowledge receipt andcomprehension of 200 OK response 1216.

Call flow 1200 may include media over cellular data 1224 between firstmobile station 702A and mobile switch 802 and may include media over TDMdata 1226 between mobile switch 802 and mobile gateway 804. In addition,call flow 1200 may include media over cellular data 1232 between secondmobile station 702B and mobile switch 802 and media over TDM 1234between mobile switch 802 and mobile gateway 804.

Exemplary 2G To IP Mode Switching Call Flow

FIG. 13 illustrates an exemplary call flow that may be used to perform2G to IP mode switching during a calling session consistent with theprinciples of the invention. Call flow 1300 may include a first dualmode mobile station 702A, an 802.11/Ethernet switch 1302 (hereinafterEthernet switch 1302), a second dual mode mobile station 702B, a mobileswitch 802, a mobile gateway 804 and a SIP proxy server 712. Firstmobile station 702A, second mobile station 702B, mobile switch 802,mobile gateway 804 and SIP proxy server 712 may be configured and mayoperate as previously described. 802.11/Ethernet switch 1302 may includeany device capable of interfacing 802.11-compatible data to anEthernet-compatible interface.

Call flow 1300 may initially include media over cellular data 1304between first mobile station 702A and mobile switch 802, media over TDMdata 1306 between mobile switch 802 and mobile gateway 804, media overcellular data 1310 between second mobile station 702B and mobile switch802 and media over TDM 1308 between mobile switch 802 and mobile gateway804. During a calling session, call flow 1300 may transition to includemedia over cellular 1340 between second mobile station 702B and mobileswitch 802, media over TDM 1338 between mobile switch 802 and mobilegateway 804 and media over IP 1334 between first mobile station 702A andmobile gateway 804. The transition from one call media to another callmedia may occur as a result of a request made by a subscriber device,such as mobile station 702A or 702B.

First mobile station 702A may perform an 802.1x authorization 1312 withEthernet switch 1302. A SIP registration 1314 may take place betweenfirst mobile station 702A and SIP proxy server 712. SIP registration1314 may employ STUN and/or TURN for traversing network devices, such asfirewalls. First mobile station 702A may issue an INVITE request 1316SIP proxy server 712. INVITE request 1316 may be an invitation to havesecond mobile device 702B join a communication session. SIP proxy server712 may send INVITE request 1318. INVITE request 1318 may include a‘Replaces’ header. SIP proxy server 712 may send message 1318 to mobilegateway 804. Mobile gateway 804 may respond with a 200 OK response 1320acknowledging receipt of INVITE request 1318. SIP proxy server 712 maysend a 200 OK response 1322 to first mobile station 702A acknowledgingreceipt of INVITE request 1316. First mobile station 702A may return anacknowledgement (ACK) message 1324 acknowledging receipt of 200 OKresponse 1322. SIP proxy server 712 may send an acknowledgement (ACK)message 1326 to mobile gateway 804 in response to 200 OK response 1320.

A BYE request 1328 may be sent from mobile gateway 804 to SIP proxyserver 712. BYE request 1328 may operate as an indication that mobilegateway 804 is going to disconnect a portion of a calling session.Mobile gateway 804 may send a release message 1330 to mobile switch 802.Disconnect message 1332 may be associated with a leg of a call. Releasemessage 1330 may cause disconnect message 1332 to be sent to firstmobile station 702A from mobile switch 802. When SIP proxy server 712receives BYE request 1328 it may respond with BYE request 1334. Mobilegateway 804 may respond with a 200 OK response 1336 in response to BYErequest 1334, and SIP proxy server 712 may send a 200 OK response 1342back to mobile gateway 804 in response to BYE request 1328. Disconnectmessage 1332 may cause first mobile station 702A to communicate usingmedia over IP 1344 between itself and mobile gateway 804.

CONCLUSION

Systems and methods consistent with the invention make possible seamlessmultimode communications using only a single SIP home server. As aresult, a user can have a single identifier, such as a phone number orURI, that can be used for communicating over wireless networks, PSTNs,IP networks, and other networks. In addition, a user does not have tomaintain separate service subscriptions with respective carriers inorder to use multimode communication techniques.

The foregoing description of exemplary embodiments of the inventionprovides illustration and description, but is not intended to beexhaustive or to limit the invention to the precise form disclosed.Modifications and variations are possible in light of the aboveteachings or may be acquired from practice of the invention. Forexample, while a series of signaling flows have been described withrespect to FIGS. 7 through 13 and while a series of acts have beendescribed with respect to FIG. 6, the order of the signal flows and/oracts may be varied in other implementations consistent with theinvention. Moreover, non-dependent signaling flows and/or acts may beimplemented in parallel.

For example, implementations consistent with the principles of theinvention can be implemented using network protocols, messagingsequences, network topologies, and communication devices other thanthose illustrated in the figures and described in the specificationwithout departing from the spirit of the invention. In addition, thesequence of events associated with communication sessions described inconjunction with FIGS. 7-13 can be performed in orders other than thoseillustrated. Furthermore, additional events can be added, or removed,depending on the specific network topologies used and the needs of usersand/or service providers. Moreover, non-dependent acts may be performedin parallel. Further, disclosed implementations may not be limited toany specific combination of hardware circuitry and/or software.

No element, act, or instruction used in the description of the inventionshould be construed as critical or essential to the invention unlessexplicitly described as such. Also, as used herein, the article “a” isintended to include one or more items. Where only one item is intended,the term “one” or similar language is used. Further, the phrase “basedon,” as used herein is intended to mean “based, at least in part, on”unless explicitly stated otherwise. The scope of the invention isdefined by the following claims and their equivalents.

1. A method for conducting a communication session involving acommunication terminal device accessing a network, the methodcomprising: at the communication terminal device, conductingcommunications corresponding to the session via a first mode of access;determining, at the communication terminal device, that a second mode ofaccess is available to be used for the communications corresponding tothe session; from the communication terminal device, sending indicationto the network that the second mode of access is to be used; and at thecommunication terminal device, conducting subsequent communicationscorresponding to the session using the second mode of access. 2-24.(canceled)